Mixing kneader

ABSTRACT

A kneader mixer comprises at least two axial-parallel rotating shafts, each of the shafts having a plurality of kneading-transporting elements axially spaced on the shaft and separated from each other on the shaft by a tubular section.

BACKGROUND OF THE INVENTION

The present invention relates to a kneader-mixer for the carrying out ofmechanical, chemical and/or thermal processes which has at least twoaxial-parallel rotating shafts on each of which there are at leastkneading and transport elements succeeding each other in the directionof rotation of the shafts, kneading and transport elements followingeach other in the axial direction of the corresponding shaft whichcontains a gap with respect to each other through which some of thekneading and transport element pass on the other shaft in each case.

Products must be treated today in many fields of industry, particularlyhowever in the chemical industry. For example, in the kneader-mixerdescribed above, two chemical products must be so intimately mixedtogether that they at least partially react. In this case, theseproducts may pass through any desired aggregate state so that therequirements made on the kneader-mixer are very high.

In essence, a distinction is made between single-shaft and double-shaftkneader-mixers. The present invention concerns a multi-spindle kneaderand mixing machine such as described, for instance, in CH-A 506 322. Inthat case, radial disk elements are present on a shaft, and axiallydirected kneading bars arranged between the disks. Kneading elementsdeveloped in frame shape engage between these disks from the othershaft. These kneading elements clean the disks and kneading bars of thefirst shaft. The kneading bars on both shafts, in their turn, clean theinner wall of the housing.

Further embodiments of multi-shaft kneader-mixers are described in EP 9210 88 29.0.

In all of these multiple-spindle mixers and kneader-mixers it is aquestion, above all, of freeing all surfaces which come into contactwith the product to be treated, and in particular, with the heatedsurfaces, from product encrustations or attachments. In theabove-mentioned European Patent Application 92 10 88 29.0, this is donealready to a substantial extent; to be sure, due to the gap between thekneading and transport elements, a ring which is not cleaned alwaysremains on the inner wall of the housing both on the agitator shaft andon the cleaning shaft.

The object of the present invention is to create a possibility for alsoeliminating this ring.

SUMMARY OF THE INVENTION

In order to achieve this object, the kneading and transport elementssucceeding each other in the direction of rotation of the shaft arearranged at least partially axially staggered.

This means that the actual kneading and transport elements for eachshaft clean the corresponding housing inner wall 100%. This hasadvantages both for the heat transfer and for the product transport.

When mention is made in the present case of kneading and transportelements, these elements have not only the kneading and transportfunction, but also the above-mentioned cleaning function.

A kneading and transport element preferably consists of a radial carrierelement and a kneading bar placed on the circumference of the carryingelement. In this connection, there is the possibility of equipping boththe radial transport element and the kneading bar in any way desired.The kneading bar can be developed in cross section in the manner of aplowshare or be provided with lateral wings. The carrying element can besegmental, disk-shaped, wrench-shaped, sawtooth-shaped, shaft-shaped ordeveloped merely as strips. Here, many possibilities are conceivable andlie within the scope of the present invention. It is merely essentialthat between the kneading elements and transport elements and here, inparticular, between the kneading bars which axially are adjacent eachother, a gap is present through which some of the kneading and transportelements pass on the other shaft. By the axial stagger of the kneadingbars from kneading and transport elements following each other in thedirection of rotation, assurance is had that this gap is continuouslycleaned.

The kneading and transport element can be placed in any desired manneron the corresponding shaft and connected with it. To be sure, thesekneading and transport elements must take up considerable forces, sothat it has been found favorable for them to be integrated into theshaft. In this connection it is possible to produce the radial carrierelements together with a ring so that this manufacturing process isconsiderably simplified. Furthermore, there is less danger of thebreaking of the radial carrier element in the case of a one-piecemanufacture. The kneading bars are then preferably welded onto theradial carrier elements.

If the connection with a ring is selected for the kneading and transportelements, the entire shaft can be developed in sections. This means thatthe shaft consists essentially of individual tubular sections betweenwhich the rings are arranged. Two adjacent rings can then possibly beseparated by an intermediate ring so that in this way the axial staggerof the kneading bars is determined. This axial stagger should in anyevent be so great that it covers the gap between the two kneading barspreceding each other in direction of rotation.

In any event, assurance must be had that in all cases those samekneading and transport elements as have the same axial stagger cooperatewith each, i.e. mesh with each other. Only in this way is the resultobtained that the two kneading bars having a different offset do notstrike against and damage each other.

In order to achieve this goal, it is necessary to adapt the number andshape of the kneading and transport elements, the speed ratio of theshafts, and the direction of rotation of the shafts to each other. It ispossible to operate the shafts both in the same direction and inopposite direction. The speed ratio of the shaft is preferably directlyproportional to the ratio of the kneading/transport bars on the shafts.Furthermore, the number of bars should be so determined that upon eachrevolution of the shaft, the same shaft transport bars are in engagementwith each other.

As a whole, by the present invention there is created a multiple-spindlekneader-mixer in which both housing inner walls are completely cleaned.This constitutes the essential advantage of the present invention, theexpense for this conversion being very slight.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and details of the invention will beevident from the following description of preferred embodiments and byreference to the drawing, in which:

FIG. 1 is a top view of a kneader-mixer of the invention, with thehousing partially cut away;

FIG. 2 is a longitudinal section through an agitator shaft in accordancewith the invention;

FIG. 3 is a developed view of the agitator shaft of FIG. 2;

FIG. 4 is a longitudinal section through a cleaning shaft in accordancewith the invention;

FIG. 5 is a developed view of the cleaning shaft of FIG. 4;

FIG. 6 is a diagrammatic view of a part of agitator shaft and cleaningshaft in position of use; and

FIG. 7 is a front view of the position of use of agitator and cleaningshaft of FIG. 6.

DETAILED DESCRIPTION

A kneader-mixer P has, according to FIG. 1, a housing which consists ofseveral housing sections 1a, 1b and 1c. The housing sections are coupledto each other by corresponding flange connections 2. Within the housingsection 1a, there is a feed pipe 3 for a product to be treated withinthe kneader-mixer and in the housing section 1c there is provided anoutlet connection 4 for the treated product.

The product is transported from the feeding connection 3 to the outletconnection 4 by means of two shafts 5 and 6 as well as kneading andtransport elements 7 arranged thereon. During the transport, a mixingand kneading of the product as well as preferably a thermal treatmenttakes place. For this purpose, the shafts 5 and 6 and possibly also thekneading and transport elements 7 as well as (not shown in detail) thehousing wall 8 are heated. For the introduction of a heating fluid intothe shafts 5 and 6 and from there possibly into the inside of thekneading and transport elements 7, connections 9 and 10 are arrangedaround corresponding inlet and outlet nipples 11 and 12 for the heatingfluid conducted through the shafts 5 and 6. A corresponding guidance ofthe heating fluid in jacket surfaces of the shafts 5 and 6 and acorresponding return through outlet nipple 12 are covered by the priorart and are therefore not further described.

Between the connections 9 and 10 journal pins 13 and 14 connected withthe shafts 4 and 5 engage through a spacer 15 a stuffing box 16 and 17against the housing 1 being provided in each case to seal off the shaft5 or 6. The journal pins 13 and 14 are coupled with each other outsidethe spacers via corresponding transmission elements 18 and 19, forinstance gear wheels, the transmission element 19 being connected viathe gearing 20 with a drive 21. Via this drive 21 and the transmission20, the transmission element 19 is first of all placed in rotation,which rotation is transmitted to the shaft 5. A transmission of thisrotary movement to the transmission element 19 can take place in thesame or opposite direction and with the same or different speed ofrotation. Corresponding stepped-down gearings are commercial and willnot be described in detail here.

In FIG. 2 it can be noted that at least a part of the agitator shaft 5is assembled of a plurality of pipe sections 30 which receive betweeneach other, at least in each case, two rings 31 and 32 which in thiscase are connected to each other via corresponding welds 33 and to thepipe sections 30. On the rings 31 and 32 there are arranged the kneadingand transport elements 7 which in each case consist essentially of akneading bar 34 and a radial carrying element 35. Particularly in FIG.7, it can be noted that the ring 31/32 and the radial carrying element35 may be made in one piece while the kneading bar 34 is placed on theradial carrying element 35. The radial carrying element 35 canfurthermore be developed in any manner desired. In the presentembodiment, it is of strip shape. However, it can also be disk-shaped,serrated, undulated, annular, segmental or the like. Only by way ofexample reference is had to Swiss Patent Applications 00551/88-0,00550/88-8, European Patent Applications 90 11 86 26.2, 91 10 54 97.1,or DE-OS 41 18 884.5.

It is essential in the present invention that the rings 31 and 32 followeach other axially so that the corresponding kneading and transportelements 7 are arranged axially offset. In this way, an axial stagger ofthe kneading bars 34 also takes place, as can be noted from FIG. 3. Oneach ring 31 or 32, there are, in accordance with FIG. 3, in each case 4kneading and transport elements 7, these kneading and transport elements7 varying in their axial stagger.

From FIG. 3 it can also be noted that, between the ring 31 and the ring32, there is also an intermediate ring 36 which spaces the rings 31 and32 so far apart that a gap 37 between two axial successive kneading bars31 is bridged over by the following kneading bar in direction ofrotation.

The cleaning shaft 6 in accordance with FIGS. 4 and 5 is also composedof pipe sections 30.1, in which connection two pipe sections 30.1 whichfollow each other in axial direction of the cleaning shaft receivebetween each other two rings 31.1 and 32.1 as well as possibly anintermediate ring 36.1. In this case also the pipe sections 30.1, therings 31.1 and 32.1, and the intermediate rings 36.1 are connected toeach other by corresponding welds 33.1.

On each ring 31.1 and 32.1 there is at least one kneading and transportelement 7.1 which also consists of a radial carrying element 35.1 and akneading bar 34.1 placed thereon. The kneading bars 34.1 or radialcarrying elements 35.1 of two corresponding rings 31.1 and 32.1 areagain arranged staggered in axial direction so that gaps 37.1 and 37.2are also axially staggered.

The manner of operation of the present invention will be explained inparticular with reference to FIGS. 6 and 7. The kneading and transportelements 7 and the kneading and transport elements 7.1 of the agitatingand cleaning shafts 5 and 6 engage in fork shape upon rotation in eachother. In this connection, the speed of rotation is so adjusted that ineach case those rotary and transport elements 7 and 7.1 which followeach other in the direction of rotation in an axially offset planeengage with each other. In this way, assurance is had that all gaps 37,37.1 and 37.2 are passed over by the corresponding kneading bars 34 and34.1 so that no ring can build up here on a housing intermediate wall orform an annular torus. In this connection, to be sure, the ratio of thenumber of kneading and transport elements on the agitator shaft to thekneading and transport elements 7.1 on the cleaning shaft is to benoted. Furthermore, the speed of the agitating and cleaning shafts 5 and6 is also to be adapted to this. If there are the same number ofkneading and transport elements 7 and 7.1 on the agitating and cleaningshafts 5 and 6, then both shafts are preferably operated with the samespeed. Insofar as only a smaller number of kneading and transportelements 7 are present on the agitator shaft (for instance 2 or 4), thecleaning shaft 6 can also be operated with a higher speed. It mustmerely be seen to it that the kneading and transport elements 7 and 7.1which are arranged staggered in a plane always cooperate with eachother.

The ratio of the number of kneading and transport elements 7 to thekneading and transport elements 7.1 on the cleaning shaft 6 is as a rulea whole integer, but a ratio of 6:4 is also possible for instance.

Furthermore, this arrangement is also possible both with the samedirection of rotation of the two shafts 5 and 6 and with oppositedirection. Direction of rotation, speed of the shafts, and number of thekneading and transport elements should be adapted to the specificproduct which is being processed by the kneader-mixer. The same appliesalso to the development of the radial carrier elements 35 and 35.1 bythe enlargement of which, for instance, the dwell time of the

I claim:
 1. A kneader for kneading and transporting a product throughthe mixture comprising:a housing having a product inlet and a productoutlet; and a pair of coaxial shafts rotatably mounted in the housingfor transporting the product from the product inlet to the productoutlet, each of the pair of coaxial shafts includes a plurality ofelements mounted thereon for kneading and transporting the productwherein the plurality of elements on each coaxial shaft are actuallyspaced thereon to provide a gap therebetween which receives a portion ofan element on the other coaxial shaft wherein each element includes aradial carrying element connected to a ring carried on a correspondingcoaxial shaft wherein adjacent rings on the coaxial shaft are separatedfrom each other by a tubular section.
 2. A kneader-mixer according toclaim 1, wherein each element consists of a radial carrying element anda kneading bar placed on the circumference of the carrying element.
 3. Akneader-mixer according to claim 2, wherein the radial carrying elementis connected with a ring which is integrated in the shaft.
 4. Akneader-mixer according to claim 3, wherein adjacent rings of adjacentelements are separated by an intermediate ring.
 5. A kneader-mixeraccording to claim 1, further including control means for rotating thecoaxial shafts at a desired speed of rotation and in a desired directionof rotation wherein the number of elements, the speed of rotation of theshafts, and the direction of rotation of the shafts are controlled sothat the elements have the same axial stagger so as to always cooperatewith each other.